Britain’s IBF welterweight champion Kell Brook said he took the fight with undisputed world middleweight champion Gennady Golovkin “to reach greatness”.
The undefeated fighters will meet in London on 10 September.
Brook, 30, who is moving up two weight divisions, is unbeaten in 36 fights while Kazakh Golovkin, 34, has won all 35 of his professional bouts.
“The greats have gone on, like Sugar Ray Leonard, to win titles in the heavier divisions,” said Brook.
“To be a great fighter, you have to do great things. For me, a welterweight, to step up against one of the most feared fighters in the world, I’ll have to do everything right. If I don’t, I’ll come up short.
“We’re going to put the hard work in in training. We will go through hell in that training camp but that’s what you have to do to reach greatness.
“When it was floated, I jumped at the chance. I’m doing it for the fans.”
American Leonard won titles at five weight divisions in the 1980s – welterweight, light middleweight, middleweight, super middleweight, light heavyweight.
Golovkin has never boxed in Britain before but has beaten two British fighters in world title defences – Matt Macklin was knocked out in three rounds in 2013 and Martin Murray lasted 11 rounds in 2015.
Speaking at a news conference in New York, he said he thinks Brook will give him his most difficult fight to date.
“It’s the biggest day for me,” he said. “He’s (Brook) very strong. It’s the biggest test for me.”